Computational and Mechanistic Studies of Pd-Catalyzed Alkene Carboacylation via Ester C-O Bond Activation

Computational and mechanistic studies of Pd-catalyzedalkene carboacylationvia ester bond activation are investigated through a combination ofdensity functional theory (DFT) and second order perturbation theory(MP2) calculations and experimental methods. The key elementary stepsof the catalytic cycle, oxidative addition, migratory insertion, transmetalation,and reductive elimination, are examined. In this paper, we proposea novel mechanism for the title carboacylation reaction; the calculationsindicate that the Pd(II) intermediate preceding migratory insertionis a cationic intermediate as opposed to the neutral metal intermediatespecies previously proposed in these types of reactions. In addition,a new organoboron species has been identified as a competent nucleophilein this transition metal-catalyzed reaction. Analysis of competingSuzuki coupling pathways reveals the carboacylation pathway to bemore energetically favorable with the appropriate selection of arylboronreagent. Experimental control studies are consistent with the computationalfindings.